Active matrix display devices, such as liquid crystal display devices and organic electroluminescent (EL) display devices, include a thin-film transistor (TFT) substrate in which TFTs are formed as switching elements or drive elements. For example, Patent Literature (PTL) 1 describes an active matrix organic EL display device including a TFT substrate.
Structures of the TFT include a bottom-gate TFT in which a gate electrode is disposed in a lower part (substrate side) of a channel layer, and a top-gate TFT in which a gate electrode is disposed in an upper part of the channel layer. For example, a silicon semiconductor or an oxide semiconductor is used as the channel layer of the TFT.
In the TFT substrate (TFT array substrate) which includes a plurality of pixels arranged in a matrix, a plurality of lines through which a signal (voltage) for driving each of the pixels is transmitted are disposed.
In recent years, due to an increase in size of a substrate following an increase in screen size of a display device, the length of lines in the TFT substrate has increased, leading to an increase in wiring resistance. For that reason, there is a demand for reducing wiring resistance.
The lines are formed using the same materials as materials of a source electrode or a drain electrode of the TFT and in the same layer as the source electrode or the drain electrode of the TFT. For that reason, the source electrode or the drain electrode is required to have a function of not only the TFT but also the line.
In view of the above, it is under consideration to employ copper (Cu) which has low resistivity as the material of the source electrode or the drain electrode, and the line.
However, Cu has low adhesion to an insulating film (interlayer insulation film) of a silicon oxide etc. In view of this, a technique of forming a Cu alloy film such as a CuMn film between a Cu line or a Cu electrode and the insulating film has been proposed (for example, PTL 1).